In general, a helmet for cycling use is very different from helmets used in automobiles or on motorcycles and usually it consists of a cap structure shaped so as to at least partially cover the head of a user and configured to protect it from bumps at the cranial portion substantially from the ocular arch up to the nuchal area, both on top and at the side.
In order to make such helmets adaptable to the various possible sizes, now there are size adjuster devices associated with the cap so that, by acting manually, it is possible to tighten the helmet on the head of the user.
In particular, such size adjusters comprise an annular structure, either closed or open in a U, arranged along the lower periphery of the cap of the helmet and able to be switched between a minimum diameter configuration and a plurality of increased diameter configurations to allow the helmet to be worn by different sized users.
The manual switching device of the configuration of the annular structure comprises a cogwheel element capable of acting on telescopic portions that form the annular structure. Disadvantageously, however, as the size varies by acting on the manual switching device, the helmet does not always sit comfortably on the head of the user.
The solution currently proposed is to equip the annular structure with support portions that, however, since they are fixed, only offer comfortable support for some sizes and not for all possible switching configurations.